Tripod type constant-velocity joint

ABSTRACT

A tripod type constant-velocity joint is proposed which is lower in cost and lighter in weight. Raceway grooves are formed in side faces of each track groove formed in the inner periphery of an outer ring and in side faces of each guide block supported by each of three trunnions of a tripod member. A plurality of rolling elements mounted between the raceway grooves are retained by retainers. The retainers have such a structure that a plurality of pockets are formed in plate members and a plurality of claws extending in opposite directions are provided on the periphery of each pocket so that it can be formed by pressing. It is thus possible to achieve reduced cost and lighter weight for a tripod type constant-velocity joint.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a tripod type constant-velocity joint in which torque is transmitted between an outer ring formed with three track grooves in its inner periphery and a tripod member mounted in the outer ring.

[0002] Tripod type constant-velocity joints are known in which three axially extending track grooves are formed in the inner periphery of an outer ring, a pair of roller guide surfaces formed in each track groove so as to oppose in the circumferential direction are cylindrically shaped, a tripod member mounted in the outer ring has trunnions at positions corresponding to the respective track grooves, and spherical rollers pivotably supported by the trunnions are arranged in the track grooves to transmit torque between the outer ring and the tripod member at the portions where the spherical rollers engage the roller guide surfaces of the track grooves.

[0003] With such a tripod type constant-velocity joint, when torque is transmitted with the outer ring and the tripod member taking a working angle, the centers of rotation of the spherical rollers are inclined relative to the length directions of the track grooves. Due to the inclination, the spherical rollers will not make a pure rolling motion, but relative slip occurs between the spherical rollers and the roller guide surfaces on the track grooves.

[0004] Therefore, frictional resistance increases at the contact portions between the spherical rollers and the roller guide surfaces, so that the slide resistance is large when the outer ring and the tripod member relatively move in the axial direction. Thus, pivoting and noise are produced and NVH properties lowers.

[0005] In order to improve the NVH properties, in a tripod type constant-velocity joint described in JP patent publication 64-5164, raceway grooves extending in the axial direction are formed in side faces of track grooves formed in the outer ring, raceway grooves are formed on both sides of guide blocks supported by trunnions of a tripod member so as to be pivotable in the moving direction of the tripod member relative to the trunnion, and a plurality of balls are mounted between the guide blocks and the outer ring to transmit torque between the outer ring and the tripod member through the balls.

[0006] In this tripod type constant-velocity joint, even when the outer ring and the tripod member take a working angle, the guide blocks are kept at a constant position by the balls mounted between the raceway grooves on the guide blocks and the raceway grooves on the outer ring. Thus, it is characterized in that when the outer ring and the tripod member relatively move in the axial direction, the balls move while rolling, so that vibration and noise are less likely to be produced and it has good NVH properties.

[0007] In the tripod type constant-velocity shown in this publication, it is necessary to provide a ball dropout preventive portion for preventing the balls from dropping out at both ends of the raceway grooves on the guide blocks. Thus, when the working angle between the outer ring and the tripod member increases, the balls will contact the dropout preventive portion, so that they cannot smoothly roll, thus producing slip. This worsens the NVH properties in the slip region.

[0008] In order to solve such a trouble, as shown in FIG. 6, a tripod type constant-velocity joint is proposed in which a plurality of balls 35 are mounted between raceway grooves 31 formed on both sides of each track groove 30 and raceway grooves 34 on both sides of a guide block 33 pivotably supported by each trunnion 33 of the tripod member to keep the position of the guide block 33, the balls 35 are retained by a retainer 36, and the moving distance of the retainer 36 is restricted to half of the moving distance of the guide block 33 by means of a moving distance restricting means to cause the balls 35 to always make a rolling motion.

[0009] In the tripod type constant-velocity joint shown in FIG. 6, when the outer ring and the tripod member transmit torque while taking a maximum working angle, the balls 35 located at both ends of the retainer 36 can come off the raceway grooves 34 of each guide block 33. Thus the retainer 36 has to be of such a structure as to prevent the balls 35 from dropping out.

[0010] Thus, with the retainer 36 in the tripod type constant-velocity joint shown in FIG. 6, the balls 35 are held by two pressed plate members 36 a, 36 b having a plurality of semispherical pockets 37 and the plate members 36 a and 36 b are coupled together by caulking a plurality of rivets 38.

[0011] In the tripod type constant-velocity joint shown in FIG. 6, since the balls 35 can always roll normally, the NVH properties are superior. But the retainer 36 is of such a structure that the number of parts is large because the two pressed plate members 36 a, 36 b are coupled together by caulking a plurality of rivets 38. Further, it is necessary to join the plate members 36 a and 36 b together so that the pockets 37 formed in the plate members 36 a and 36 b will align. Thus it is extremely troublesome to assemble the retainer 36 and the cost is high. Thus, improvement is desired in achieving reduced cost and lighter weight for a tripod type constant-velocity joint.

[0012] An object of this invention is to provide an improved tripod type constant-velocity joint which is superior in NVH properties, low in cost and light in weight.

SUMMARY OF THE INVENTION

[0013] According to this invention, there is provided a tripod type constant-velocity joint comprising an outer ring, a tripod member mounted in the outer ring, the outer ring being formed with three axially extending track grooves in inner periphery thereof, straight raceway grooves formed in side faces of the each track groove so as to extend in the axial direction of the outer ring and circumferentially oppose each other, the tripod member having three trunnions at positions corresponding to the track grooves, guide blocks supported by the respective trunnions in the track grooves so as to be pivotable relative to the trunnion in the moving direction of the tripod member, the guide blocks each being formed with a pair of raceway grooves on both sides thereof so as to oppose the raceway grooves formed in the each track groove, a plurality of rolling elements mounted between the opposed raceway grooves, retainers for retaining the rolling elements, and a moving distance restricting unit for restricting the moving distance of the retainers to half of the moving distance of the guide blocks, characterized in that the retainers comprise plate members each made of metal and formed with a plurality of pockets to receive the rolling elements, and a plurality of claws are provided on the periphery of the each pocket and raised in opposite directions, whereby the rolling elements are mounted in the pockets while elastically deforming the claws.

[0014] Since the retainers have such a structure that a plurality of pockets for receiving the rolling elements are formed in plate members and a plurality of jaws are provided on the periphery of each pocket so as to extend in opposite directions, easy-to-manufacture, lightweight retainers are provided, so that it is possible to achieve reduced cost and lightness in weight.

[0015] Since the rolling elements are mounted in the pockets while elastically deforming the claws, the rolling elements are prevented by the claws from coming out, so that it is possible to reliably retain the rolling elements. By providing two claws on the periphery of each pocket at opposed positions so as to extend in opposite directions, it is possible to prevent the rolling elements from coming out.

[0016] Further, by providing four claws on the periphery of each pocket at 90° intervals so that first set of two claws and the second set of two claws extend in opposite directions, it is possible to reliably prevent the rolling elements from coming out.

[0017] In the tripod type constant-velocity joint according to this invention, by forming the retainers by pressing, it is possible to achieve further reduction in cost of the constant-velocity joint.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other features and objects of the present invention will become apparent from the following description made with reference to the accompanying drawings, in which:

[0019]FIG. 1 is a partially cutaway front view showing an embodiment of the tripod type constant-velocity joint according to this invention;

[0020]FIG. 2 is a sectional view along line II-II of FIG. 1;

[0021]FIG. 3 is a perspective view showing retainers of the same;

[0022]FIG. 4 is a partially cutaway front view of another embodiment of the tripod type constant-velocity joint;

[0023]FIG. 5 is a perspective view showing retainers of the tripod type of constant-velocity joint of FIG. 4; and

[0024]FIG. 6 is a transverse sectional plan view showing a conventional tripod type constant-velocity joint.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0025] Embodiments of this invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, three axially extending track grooves 2 are formed in the inner periphery of an outer ring 1 at intervals of 120°. In side faces of each track groove 2 opposing in a circumferential direction, axially extending raceway grooves 3 are formed.

[0026] A tripod member 4 mounted in the outer ring 1 is provided with three trunnions 5 at positions corresponding to the track grooves 2. A guide block 6 is supported by each trunnion 5. In order to support the guide blocks 6, a spherical surface 5 a is formed on each trunnion 5, and the trunnions are inserted in cylindrical holes 7 formed in the respective guide blocks 6 so that the trunnions 5 and the guide blocks 6 will be pivotable in any direction relative to each other.

[0027] A pair of raceway grooves 8 are formed on both sides of each of the guide blocks 6 so as to oppose the raceway grooves 3 formed on both sides of each of the track grooves 2.

[0028] On both sides of the guide blocks 6, a plurality of rolling elements 9 are arranged in the axial direction of the outer ring 1 and retained by retainers 10. A pair of retainers 10 on both sides of each guide block 6 are coupled by a coupling plate 13 (FIG. 3) mounted between an inner surface 11 of each track groove 2 and an outer surface 12 of each guide block 6.

[0029] As shown in FIGS. 2 and 3, each retainer 10 comprises a plate member 14 formed with a plurality of pockets 15 for receiving the rolling elements 9. At opposite positions of the periphery of each pocket 15, a pair of claws 16 a, 16 b are formed. One of the claws 16 a is raised to outer side of the plate member 14, while the other claw 16 b is raised to inner side thereof so as to face away from each other.

[0030] Each rolling element 9 is mounted in the pocket 15 while elastically deforming one of the pair of claws 16 a, 16 b. In this state, the rolling elements 9 are prevented from coming out of the pockets 15 by the claws 16 a, 16 b.

[0031] The retainers 10 having such a structure are formed by pressing a metallic plate. In pressing step for the plate members 14, a plurality of pockets each formed with a pair of claws are simultaneously punched, and the pair of claws of each pocket are bent in opposite directions by a bending punch inserted into the pocket from one side of the plate member 14 and another bending punch inserted from the other side.

[0032] As shown in FIG. 3, if each pair of retainers 10 are integrally formed at both ends of the coupling plate 13, a blank is punched so that the plate members 14 are integrally formed at both ends of the coupling plate 13, and a plurality of pockets each formed with the pair of claws at opposed positions are simultaneously punched in each plate member 14. The pair of claws of each pocket are raised in opposite directions and the plate members 14 are bent in the same direction relative to the coupling plate 13.

[0033] By mounting a plurality of rolling elements 9 between the raceway grooves 3 formed on both sides of each track groove 2 and the raceway grooves 8 formed on both sides of each guide block 6, it is possible to keep the position of the guide blocks constant. When the outer ring 1 and the tripod member 4 take a working angle, slip occurs at the contact portions between the spherical outer surfaces 5 a of the trunnions 5 and the cylindrical inner surfaces of the guide blocks 6, so that the trunnions 5 will incline or pivot relative to the axes of the cylindrical holes 7 of the guide blocks 6.

[0034] Thus, when torque is transmitted while the outer ring 1 and the tripod member 4 take a working angle, the guide blocks 6 move along the track grooves 2 in the axial direction of the outer ring 1 with their positions kept constant.

[0035] During movement of the guide blocks 6, the rolling elements 9 will move while rolling due to contact with the raceway grooves 3 and 8, so that the moving resistance of the guide blocks 6 is extremely small. Thus, the guide blocks 6 can slide smoothly without producing vibration while sliding.

[0036] The moving distance of the rolling elements 9 during sliding of the guide blocks 6 is about half of the moving distance of the guide blocks 6 if slipping at the contact portions on the raceway grooves 3 and 8 is ignored. If a difference in the moving distance is produced between the rolling elements 9 and the retainers 10, the rolling elements 9 will slip, thus producing vibration.

[0037] Also, if the retainers 10, which retain the rolling elements 9, are simply mounted between the sides of the track grooves 2 and the sides of the guide blocks 6, the rolling elements 9 can slip at the contact portions between the rolling elements 9 and the raceway grooves 3 and 8, or the retainers 10 can displace in the axial direction and come out of position due to vibration of the vehicle on which is amounted the constant-velocity joint.

[0038] In order to cause the rolling elements 9 to make a pure rolling movement and prevent them from dropping out of the raceway grooves 3 and 8, the moving distance of the retainers 10 is restricted to half of the moving distance of the guide blocks 6 by means of a moving distance restricting mechanism 20.

[0039] As shown in FIGS. 1 and 2, the moving distance restricting mechanism 20 has a pair of inclined grooves 21 a, 21 b elongated in the axial direction of the outer ring 1 and inclining in opposite directions. They are formed in the inner surface 11 of each outer ring track groove 2. On the axially outer surface of each guide block 6 at positions opposing the inclined grooves 21 a, 21 b, a pair of inclined grooves 22 a, 22 b inclining in opposite directions to the inclined grooves 21 a, 21 b are formed.

[0040] A ball 23 is received in each intersecting portion of the inclined grooves 21 a, 21 b on the outer ring 1 and the inclined grooves 22 a, 22 b on the guide blocks 6. The balls 23 are supported in a pair of guide grooves 24 (FIG. 3) formed on both sides of the coupling plate 13. The guide grooves 24 are elongated in the direction perpendicular to the moving direction of the retainers 10. The balls 23 are movable along the guide grooves 24.

[0041] As described above, by forming the oppositely inclining inclined grooves 21 a, 21 b, 22 a and 22 b in the inner surface 11 of each track groove 2 and the axially outer surface 12 of each guide block 6, respectively, and supporting the balls 23 received in the intersecting portions of the inclined grooves 21 a, 21 b, 22 a and 22 b in the guide grooves 24 formed in each coupling plate 13 so as to be movable in a direction perpendicular to the moving direction of the retainers 10, the balls 23 will move by half of the moving distance of the guide blocks 6 due to contact with the inclined grooves 21 a, 21 b, 22 a and 22 b as the guide blocks 6 move along the track grooves 2. Thus, the retainers 10 also move by half of the moving distance of the guide blocks 6, so that they will move by the same amount as the moving distance of the rolling elements 9, which move while rolling due to contact with the raceway grooves 3 and 8.

[0042] Thus, the rolling elements 9, which are subjected to loads, are always in a rolling state, so that it is possible to achieve good NVH properties over the entire sliding region.

[0043] Also, between the inner surface 11 of each track groove 2 and the axially outer surface 12 of each guide block 6, a space has only to be provided to receive the balls 23 and the coupling plate 13 for coupling each pair of retainers 10. Thus it is possible to avoid the increase in the size of the outer ring 1. This makes it possible to provide a compact constant-velocity joint.

[0044] The moving distance restricting mechanism 20 for restricting the moving distance of the retainers 10 to half of the moving distance of the guide blocks 6 is not limited to the embodiment shown.

[0045] As shown in FIGS. 1 and 3, the retainers 10 for supporting a plurality of rolling elements 9 have such a structure that a plurality of pockets 15 are formed in the plate members 14 and a pair of claws 16 a, 16 b, which extend in opposite directions, are provided at opposed positions of the periphery of each pocket 15. Compared with a conventional retainer in which two pressed metallic plates are joined together by caulking rivets, a retainer is provided which is small in the the number of parts, easy to manufacture, low in cost, and lightweight.

[0046] Thus, it is possible to achieve reduced cost and lighter weight for a tripod type constant-velocity joint.

[0047] Also, by mounting each rolling element 9 in the pocket 15 while elastically deforming one of the pair of claws 16 a and 16 b, it is possible to stably hold the rolling elements 9 and prevent them from coming out.

[0048]FIGS. 4 and 5 show another embodiment of retainers 10 for retaining a plurality of rolling elements 9. In this embodiment, four claws 16 a, 16 b are formed on the periphery of each of the pockets 15 formed in the plate member 14 at intervals of 90°. Two claws 16 a arranged at opposed positions are raised to one side of the plate member 14 and the remaining two claws 16 b are raised to the other side thereof to prevent the rolling elements 9 mounted in the pockets 15 from coming out.

[0049] By providing four claws 16 a and 16 b on the periphery of each pocket 15, it is possible to stably retain the rolling elements 9 and more reliably prevent them from coming out.

[0050] As described above, according to this invention, because the retainers for retaining a plurality of rolling elements are of such a structure that a plurality of pockets are formed in a single metallic plate member and a plurality of claws extending in opposite directions are formed on the inner periphery of each pocket, it is possible to provide retainers that are low in cost and lightweight. Thus, it is possible to achieve reduced cost and lightness in weight for a tripod type constant-velocity joint. 

What is claimed is:
 1. A tripod type constant-velocity joint comprising an outer ring, a tripod member mounted in said outer ring, said outer ring being formed with three axially extending track grooves in inner periphery thereof, straight raceway grooves formed in side faces of said each track groove so as to extend in the axial direction of said outer ring and circumferentially oppose each other, said tripod member having three trunnions at positions corresponding to said track grooves, guide blocks supported by said respective trunnions in said track grooves so as to be pivotable relative to said trunnion in the moving direction of said tripod member, said guide blocks each being formed with a pair of raceway grooves on both sides thereof so as to oppose said raceway grooves formed in said each track groove, a plurality of rolling elements mounted between said opposed raceway grooves, retainers for retaining said rolling elements, and a moving distance restricting unit for restricting the moving distance of said retainers to half of the moving distance of said guide blocks, characterized in that said retainers comprise plate members each made of metal and formed with a plurality of pockets to receive said rolling elements, and a plurality of claws are provided on the periphery of said each pocket and raised in opposite directions, whereby said rolling elements are mounted in said pockets while elastically deforming said claws.
 2. A tripod type constant-velocity joint as claimed in claim 1 wherein said claws comprise four claws and a first opposed pair of claws and a second opposed pair of claws extend in opposite directions to each other.
 3. A tripod type constant-velocity joint as claimed in claim 1 or 2 wherein said retainers are made by pressing. 